Oskar Heil Speakers Aulos

The Aulos Loudspeakers $3100
Specifications Speaker Elements: 1 A.M.T. mid range tweeter 1500 - 23000 Hz 1 15 cm bass unit 40 - 1500 Hz Total Frequency Response: 40 - 23000 Hz Sensitivity: 89 dB 1 W 1 meter Amplification Requirements: 50 - 200 W System Type: Bass reflex Impedance: 4 ohm minimum Cabinet finish: Oiled walnut, cherry or black maple veneer Dimension including grill W/D/H: 23 x 30 x 50 cm Weight: 8.7 Kg.


Review by by Neil Walker Review Summary Sound  "No question these are musical speakers -- easy to listen to, capable and charming as they bring out the beauty and emotion I seek from music." Features  Heil AMT driver along with a 6" woofer; unique styling and cabinet with real-wood veneer. Use  Ditch the grilles for serious listening as they degrade the sound noticeably. Value.   Many speakers these days look downright odd. The average consumer wants to see a 10" chromium or clear polypropylene woofer surrounded by an array of metallic-cone midranges and tweeters. But a speaker that resembles a hooded monk at prayer or Darth Vader with metal pipes for legs is not going to fulfill the average listener’s fantasy of high-tech gizmos. However, now that I am growing accustomed to the unusual and the arcane in speaker design, I was beginning to think that I had seen it all.
Just in time to reassure me that I had not seen everything in the area of unusual design, along comes the Oskar Heil Aulos. With its grille in place, it looks fairly ordinary. But once the grille is off, it really stands out.
Technical description
When you remove the speaker's grille, you have to defy the laws of physics; that is, you have to allow it to bend so that you can wiggle out the little plastic pegs that hold it in place. Imagine an L attached at both ends. There is no way you can install or remove such a structure without breaking the L or snapping one of the pegs (which had already happened to one of the speakers I received for review).
Once you have the grilles off, leave them off except for shipping or for repelling the inquisitive hands of curious two-year-olds. The Aulos's grille definitely degrades the sound. Once you have it off, you can appreciate what makes this speaker so unusual. The tweeter, also known in this configuration as an Air Motion Transformer (AMT) or Air Velocity Transformer (AVT), appears to be little more than a small rectangular plate filled with what appear to be horizontal ventilation slots, each attached vertically to the speaker enclosure just above the upward-pointing woofer. It covers the range from 1500-23000Hz. The woofer is set at a 45-degree angle to maintain correct phasing. This 6" driver is claimed to respond within +/- 3dB from 40Hz to the crossover point of 1500Hz.
This tweeter is the product of genius. It is the design of Dr. Oskar Heil, a physicist who invented the field-effect transistor. We learn from Précide S.A., the Swiss manufacturer of the driver, that Dr. Heil began his research into loudspeaker design by studying "…how nature designed and constructed the human ear. Then his studies concentrated on animals of a small proportion, which can produce a loud sound, especially compared to their size. These studies led to Dr. Heil’s formulation of his basic diaphragm design theory and the subsequent development of the Oskar AVT (AMT) Air Velocity Transformer."
The unique design feature of the OSKAR AVT, which distinguishes it from all other speakers, is an extremely lightweight diaphragm, folded into a number of accordion-like pleats to which aluminum foil strips are bonded. The diaphragm is mounted in an intense magnetic field and a music signal is applied to the aluminum strips. This causes the pleats to alternately expand and contract in a bellows-like manner in conformance with the music signal, forcing air out of the pleats and sucking in on the other side. The air movement is five times greater than the movement of the membrane; therefore the velocity must also be five times greater. The total moving mass is approximately 1 gram, and we have therefore an almost perfect transducer system. The AVT multiplies (transforms) the air motion by a factor of 5.3 (with a total mass of less than 1 gram) and is, therefore, appropriately called an Air Velocity Transformer.
The cabinet of the speaker is constructed of MDF, and a high-quality wood veneer covers it on all sides. While the wood veneer is attractive and quite conventional, the bass ports (yes, ports, as in two of them) on the front of the speaker are unique. Instead of the usual big hole, there are two round ports 1" in diameter.
This moderately sensitive speaker earns a manufacturer’s claim of 89dB/W/m sensitivity. Its impedance of 4 ohms and sensitivity presented no problems whatsoever for the Audiomat Arpège integrated amplifier’s push-pull EL34s at 30Wpc. At all volume levels, the sound remained clear and undistorted, and at low volume it still presented a reasonable soundstage and low-frequency response.
At 19 pounds, with dimensions of 9"W by 11.8 "D x 20"H, this speaker, as odd as it may look to some, is easy to place, attractive with its real-wood finish (oiled walnut, cherry or black maple veneer are the choices) and is family-room friendly.